Project Summary Voltage-gated potassium (Kv) channels are generated by tetramers of pore-forming ? subunits, often in complexes with other, non-pore-forming ? subunits. This project is focused on two highly important, 5-member families of Kv channel subunits: the KCNQ ? subunits and the KCNE ? subunits. KCNQ1 is essential in the heart and numerous epithelia; its diverse physiological roles in both excitable and non-excitable cells are facilitated by interaction with each of the 5 KCNE single-transmembrane domain ? subunits. KCNE ? subunits are widely expressed and regulate ? subunits from most Kv subfamilies, and even other channel types. KCNQ2-5 ? subunits, especially KCNQ2/3 heteromers, are best known for their essential role in generating the neuronal M-current, which regulates neuronal excitability. KCNQ2-5 are also expressed in other tissues, including the vasculature and auditory system. Reflecting their physiologic importance, disruption of KCNQ or KCNE genes causes disorders as diverse as cardiac arrhythmia, diabetes, achlorhydria, hypothyroidism, and epilepsy. We use a highly integrated approach to investigate the molecular mechanistic bases for KCNQ and KCNE biology and pathophysiology. This includes both knockout and knock-in mouse models, cellular electrophysiology, transport and radioligand assays, transcriptomics, various imaging modalities, structure- function and biochemical techniques. In the next five years, we aim to address several outstanding challenges in the field, pursuing the following novel research directions. (1) Inherited disorders linked to KCNQ or KCNE genes are often highly complex, multi-system diseases because the genes are typically expressed in multiple tissues. Yet, traditional approaches often involve focusing on a single tissue. We aim to dissect the basis for KCNQ- and KCNE-based diseases by embracing multi-system approaches and by first understanding the molecular basis for the intertwining physiological functions of these subunits. (2) We recently found that KCNQ channels form physiologically essential complexes with several different types of sodium-coupled solute transporters. We will study the molecular mechanisms and roles of novel signaling nanodomains created by ?chansporter? complexes. (3) We very recently discovered that some neurotransmitters and their analogs can directly activate specific neuronal KCNQs, a paradigm shift with potentially widespread ramifications. We will investigate its physiological relevance, molecular mechanisms, and crosstalk with co-assembled transporters. (4) We will pursue the molecular basis and physiological importance of several newly discovered KCNQ and KCNE interactions involving, e.g., Amyloid Precursor Protein C99 fragment, and the focal adhesion protein, Testin. Work in this project will dissect the rich repertoire of signaling facilitated by ion channels containing KCNQ and/or KCNE subunits, in a variety of different organ systems and cell types. The goals are to understand the mechanisms underlying KCNQ/KCNE-linked biological processes, and elucidate how they are perturbed in disease states, and how they can be leveraged to develop safer, more effective therapeutics.